The invention relates to a device for fastening an airbag module in a vehicle.
For fastening airbag modules a plurality of different spring detent systems are known in which a latching hook formed at the airbag module or at the steering wheel is secured against falling out by means of a detent spring disposed at the steering wheel or at the airbag module. In all these systems—DE 299 08 967 is cited by way of example—the spring made of round spring wire having a minimum diameter of about 2-3 mm is bent so as to be capable of withstanding the forces upon release of the airbag and of safely holding the module at the steering wheel.
Springs of this type have the drawback, however, that during assembly the module can be pressed into its acceptance at the steering wheel only with considerable effort so as to press the spring arms out of their idling condition into a position in which the latching hooks can bypass them to get into their mounting position. This requires additional checks as to whether all latching hooks are correctly engaged.
In order to overcome these drawbacks when assembling airbag modules with such conventional wire springs, applicant's EP 2 145 801 A1 suggested a generic fastening device. Instead of the round wire spring, a U-shaped spring made of flat iron being movably supported on a plate and having two parallel especially long arms was suggested. The freedom of movement of the spring was limited, on the one hand, by bridge-like elements and, on the other hand, by pins so that when inserting the latching hook through a passage opening of the plate initially the entire spring performed a rotation and subsequently either of the arms was deflected. By displacing the spring as a whole in its holder (without compressing the latter) the individual relatively long spring arm provided for engaging a latching hook then had to be deflected to a small extent only. In this way the effort of assembling the airbag module could already be considerably reduced.
However, with this type of fastening an unhindered low-friction mobility of the spring on the plate had to be ensured, in particular the spring had to be adapted to be rotated as a whole during assembly; therefore play had to be provided. Moreover tolerance limits have to be strictly observed in the dimensions and the arrangement of the passage opening, the bridge-like elements and the pins relative to each other as well as in the shape of the spring (bending) so as to prevent the risk of jamming of the spring, especially before engagement. This entailed an expensive manufacture. Further the rotation of the spring requires a large space in the receiving chamber of the module.